The goal of the present study is to precipitate and characterize cognitive dysfunction in mild to moderate MS patients and compare them with healthy controls. By examining cognitive deficits in MS before and following a mentally fatiguing task, we hope to establish a better understanding of the extent and nature of their cognitive deficits and determine the efficacy of our neuropsychological battery for use in clinical trials. Primary Outcomes Measures: Change Outcome Measures: Change in verbal memory (Total Recall score on the SRT) (Selective Reminding Test). Secondary Outcome Measures: Will examine other areas of cognitive function measured by our neuropsychological battery and descriptive measures of the MS patients such as disability level (EDSS), cognitive complaints(MAS-Q), fatigue(FSS) and level of depression (MADRS).